The centre axis of Maeshowe's inner entrance passage is directly aligned with the centre of the Barnhouse Stone.

From Maeshowe, the line travels out to strike Hoy's Ward Hill at a place where the sun sets 22 days before and after the midwinter solstice.

This three-week period is referred to by archeoastronomers, such as Alexander Thom, as a megalithic month - a sixteenth of a year.

Whether this alignment meant that the stone was put in place at the same time Maeshowe was built or was a later addition, erected to mark the alignment, is not clear.

The discovery of a socket hole to the rear of Maeshowe, that would once had housed another stone, seems to indicate that the Barnhouse Stone did have some function in the ritual use of the chambered cairn.

What makes this phenomenon interesting is the fact that if, as has been suggested, the Barnhouse Stone was an outlier to the Stenness ring and a part of the ceremonial complex, we have a definite link between the ceremonies held at the stone rings and in Maeshowe.